A uniform basement: Implications for the tectonics of Beishan Orogenic Belt in the southern Central Asian Orogenic Belt

Abstract

The orogen is a significant window for studying the history and architecture of Earth; its architecture involves many significant issues. Currently, research on the architecture of orogenic belts mainly focuses on the process of orogeny, and few studies focus on the tectonics before the orogeny, which somewhat constrains orogen evolution. The nature of the basement(s) of microcontinents in the Beishan Orogenic Belt (BOB) in the middle Central Asian Orogenic Belt (CAOB) has been debated for a long time, which causes confusion about the tectonics of the BOB. This study conducted field surveys, geochronology, geochemistry, and Hf isotope analysis on the major microcontinents of BOB. The age information of ca. 1.4 Ga and the Paleoproterozoic-Archean with small scale were found in the northern BOB. The northern BOB (NBOB) and southern BOB (SBOB) (separated by the Hongliuhe-Niujuanzi-Xichangjing ophiolitic mélange belt) have experienced similar magmatic thermal events at ca. 1.4 Ga and ca. 0.9 Ga, which are revealed by the analogical tectonic setting, formation ages, and Hf isotopic features. The Precambrian basements of the NBOB and SBOB are analogous in terms of rock assemblages, detrital zircon ages, magmatic rock ages, εHf(t) of Precambrian rocks, and Hf crustal model ages TDMC of Paleozoic igneous rocks, which imply that they shared similar history and provenance and might originate from a uniform basement. The basement has no close tectonic affinity to the adjacent cratons or blocks, except the Baltica Craton and Laurentia Craton. And it might have been involved in the amalgamation of the Columbia Supercontinent and be situated on the periphery of the Rodinia Supercontinent, and then fragmented when the Rodinia Supercontinent rifted apart.